> > is there a way to have a model subclass avoid the creation of a > > new database table,and just take its data straight out of the table for > > its superclass? > > Right now, I suspect you would also have to manually set Meta.db_table > and some things like that. However, I strongly suspect each of those are > fairly straightforward to sort out. We can set db_table automatically > for such models, if it's not set. We have to make sure the pk property > talks to the first ancestor model, too. Basically a bunch of fiddly > stuff, but nothing that's brain surgery levels of difficulty.
Following Malcolm's tips, I have managed to get this working. After
applying the patch from ticket #3163, I've formulated this class
decorator to make the necessary tweaks to the model's meta info:
def virtual_inheritance(cls):
base = cls.__bases__[0]
pk = base._meta.pk
# don't create a new db table
cls._meta.managed = False
# use the superclass table name
cls._meta.db_table = base._meta.db_table
# remove the auto-created parent reference
cls._meta.local_fields[:] = []
# use the superclass primary key
cls._meta.pk = pk
cls._meta.parents[base] = pk
Now I can do the following:
class MyUser(auth.models.User):
def an_extra_method(self):
print "hooray!"
virtual_inheritance(MyUser)
The resulting model behaves exactly as I wanted, adding functionality to
the default User model but taking its data straight out of the auth_user
table.
If I'm feeling inspired tomorrow, I might try to formulate similar logic
as a patch to the ModelBase metaclass, so that subclasses that don't add
any fields will get pure-python inheritance by default. In the
meantime, I hope some other people might find this trick useful.
Cheers,
Ryan
--
Ryan Kelly
http://www.rfk.id.au | This message is digitally signed. Please visit
[email protected] | http://www.rfk.id.au/ramblings/gpg/ for details
signature.asc
Description: This is a digitally signed message part
